Helicopter carried dump-buckets are well known for use in fighting forest fires. These buckets, at their simplest, may comprise a rigid or flexible reservoir or body for holding a volume of water, a sling to suspend the reservoir from a helicopter, a valve, and an actuator which is controlled from inside the helicopter to operate the valve to release the water from the reservoir over the fire.
In some prior art buckets, the valve may consist of a simple flapper valve located on a bottom interior surface of the reservoir and operated by a remotely controlled actuator, for example. A flapper valve typically includes a base plate having an outlet therein, a flat flapper member disposed over-top of the base plate so as to block the outlet, and a hinge connected between an edge of the flapper member and the base plate to hingeably connect the flapper member to the base plate permitting the flapper member to alternately block and expose the outlet.
In other prior art buckets, the valve may consist of a butterfly valve, which typically includes a longitudinally extending axle having first and second coplanar plates extending laterally therefrom. The butterfly valve may be connected to a bottom portion of the bucket and located in an opening therein. When closed, the first plate may seal against an interior surface of the bucket while the second plate may seal against an exterior surface of the bucket. The valve may be opened by rotating the first and second plates about the axle and may be fully opened by rotating the plates to a position perpendicular to their closed position.
There are problems associated with each of these valves. With the flapper vales, there are significant forces imparted to the valve by a full head of water that tend to resist the hinging of the flapper member and thereby resists the opening of the flapper valve, which requires a powerful motor to actuate the flapper, resulting in increased weight and power consumption. High electrical power demands in a helicopter is undesirable since the onboard equipment need to undergo rigorous testing and certification, and the associated cabling needed for such high demands increases the weight of the equipment substantially. Furthermore, the operation of the flapper valve may create turbulent flow, causing the water to disperse laterally as it is dumped. In fire-fighting, lateral dispersal may be undesirable as the water may be more susceptible to evaporation before reaching the ground and also because some of the water may overshoot the desired target. With the butterfly valves, they tend to cause lateral dispersal when operated as a metering valve and may be difficult to seal as one plate may be located inside the bucket and the other plate may be located outside the bucket.
To address some of the shortcomings of flapper valves and butterfly valves, U.S. Pat. No. 6,192,990 to Brooke discloses a multi-dump metering valve having an outer assembly and an inner assembly in which the outer assembly is moveable between open and closed positions, and the outer assembly has a reduced surface area on those surfaces which are disposed normally to a direction of movement. The outer assembly is thereby adapted to be less affected by hydrostatic and hydrodynamic forces directed so as to oppose its movement. U.S. Pat. No. 6,192,990 is in its entirety incorporated herein by reference. While the subject matter disclosed in Brooke is an improvement over the prior art, nevertheless, it would be desirable to even further reduce the surface area on those surfaces which are disposed normally to a direction of movement so as to be even less affected by hydrostatic and hydrodynamic forces directed so as to oppose its movement. With an even further reduced surface area, the force required to actuate the valve would be considerably less with the advantage that the actuating hardware may be reduced to achieve considerable weight reduction and that motors with a reduced power demand may be used with the advantage of a reduced electric power demand. In addition, it would be desirable for the valve apparatus to be more easily serviceable so that the seals in the apparatus are more easily replaced when worn or damaged.